1. Field of the Invention
This invention relates to the preparation of a reaction injection molded (RIM) microcellular polyurethane elastomer. It more particularly relates to the preparation of a reaction injection molded polyurethane elastomer employing heteric or internal block ethylene oxide polyols.
2. Description of the Prior Art
The automotive industry is faced with legislative mandates which require continued improved fuel economy. In order to achieve these higher fuel economy goals, the automotive industry has downsized large vehicles. Furthermore, the automotive industry has investigated the use of lower weight materials. Among the types of materials which may be employed are those produced by reaction injection molded polyurethanes. In order for these products to meet the demanding requirements for their application. they must be sufficiently rigid to be self supporting, have thermal dimensional stability to allow for normal processing operations at elevated temperatures, have low coefficients of thermal expansion, have a class A surface and good paintability, and enjoy good impact characteristics at low temperatures.
U.S. Pat. No. 3,892,691 teaches the preparation of polyurethane products employing quasi prepolymers of diphenylmethanediisocyanate and dipropylene glycols together with a polypropylene ether triol such as is prepared by the reaction of ethylene and propylene oxide with trimethylolpropane or glycerol and the use of the chain extender 1,4-butanediol.
U.S. Pat. No. 4,243,760 teaches the preparation of reaction injection molded polyurethane products by employing chain extending agents such as ethylene glycol. propylene glycol and 1,4-butanediol.
U.S. Pat. No. 4,102,833 also teaches the preparation of reaction injection molded urethanes by employing long chain polyols together with a short chain diol or triol such as ethylene glycol or glycerol.
The prior art also teaches the use of diethyltoluenediamine as a chain extender instead of ethylene glycol or butanediol.
U.S. Pat. No. 4,379,105 teaches the preparation of polyurethane elastomers employing a mixture of ethylene oxide tipped and propylene oxide tipped polyoxyalkylene polyether polyols.